The present invention relates to holding devices for sensors, and more particularly relates to a thermistor assembly received within a plastic holder and secured to a module by a locking mechanism.
Traditional automotive cooling systems include a compressor, a condenser and an evaporator. The compressor is a belt driven pump that is fastened to an engine. The compressor compresses and transfers refrigerant gas. It has an intake side and a discharge side. The intake side draws in refrigerant gas from the evaporator and discharges the refrigerant gas to the condenser. Hot, compressed refrigerant gas enters the top of the condenser and is cooled. As the gas cools it condenses and is discharged at the bottom of the condenser as a high-pressure liquid. The high-pressure liquid is converted to a low-pressure liquid and transferred to the evaporator. The evaporator receives the low-pressure liquid. Because of very low boiling points, warm air passing through the evaporator fins causes the refrigerant to boil. The boiling refrigerant absorbs large amounts of heat and is discharged to the compressor to repeat the cycle.
The evaporator must be maintained at a proper temperature to make the refrigerant liquid boil. For a typical refrigerant such as R12, the evaporator temperature should be 32xc2x0 Fahrenheit or 0xc2x0 Celsius. If the evaporator becomes too cold, the evaporator coil will freeze. A frozen evaporator coil will not absorb as much heat and the efficiency of the cooling system will be greatly reduced.
To maintain the proper temperature and prevent freezing of the evaporator coil, a control system in the automobile monitors the temperature of the evaporator. Traditionally, a sensor, such as a thermistor enclosed in a sensor case, is placed near the evaporator to measure the ambient air temperature surrounding the evaporator coil. The sensor transmits data to the control system through a cable. To maintain the sensor in the proper location during operation of the automobile, a clip is attached to the sensor case. The clip is then snapped into the evaporator core at a designated location.
The use of the clip to secure the sensor case in the proper position near the evaporator core has presented several problems. First, a large amount of force is required to push or snap the clip into the evaporator core. This poses an ergonomic issue when assembling the automobile HVAC unit during mass production. Secondly, to service or replace the sensor the entire cooling system must be disassembled to reach the sensor. This disadvantage requires costly repair services to replace a relatively inexpensive sensor. Thirdly, to properly locate the sensor in the cooling system, a gage is required to attach the clip to the sensor case. Again, this problem requires additional assembly time and is a burden in mass production. Finally, because the clip only secures the sensor, the cable used to transmit the measurements to the control system is exposed in the cooling system. Through the assembly process or normal use of the automobile the cable can be pinched or sliced open by the numerous parts of the cooling system. This problem causes damage to the overall operation of the system. The sensor could fail to transmit measurements, thereby allowing the evaporator coil to freeze.
Accordingly, we propose an alternative technique of attaching a sensor for measuring the temperature of ambient air surrounding an evaporator of a cooling system that permits easy installation in a manufacturing environment and prevents damage to the sensor.
The present invention includes a holder and a locking mechanism for securing a sensor assembly in a proper position in an HVAC unit. The holder includes two longitudinal members with channels disposed in each member. The channels of each member narrow at one end of the longitudinal member. The channels receive the sensor assembly including a thermistor and a cable. The longitudinal members also include a projection and a slot. When the projection is inserted into the slot the channels of the two longitudinal members form a cavity for receiving the sensor assembly, thereby encapsulating the sensor assembly. One end of the holder also includes a locking projection and a knob. The locking projection is utilized to secure the holder to the locking mechanism.
The locking mechanism is coupled to the side of the HVAC unit or cooling system. It includes a base and a locking plate with a locking channel disposed there between. The holder is received in an aperture disposed throughout the base and locking plate. The locking projection of the holder is received by the locking plate through an opening and secured in the locking channel. The knob is used to actuate a twist-and-lock feature of the locking mechanism.
An advantage of the present invention is that the sensor assembly is easily positioned and secured within the HVAC unit without the need for a gage or measuring device.
Another advantage of the present invention is that the holder and sensor can be easily removed from the HVAC unit without disassembling the entire unit.
A further advantage of the present invention is that the cable is secured within the holder thereby reducing the possibility for pinching or damaging the cable.